HMS

• Handheld, Manpack, Small Form Factor radio transceivers in the United States' military Joint Tactical Radio System
• Hans Majestäts Skepp (His Majesty's ship) or Hennes Majestäts Skepp (Her Majesty's Ship), the prefix of Royal Swedish Navy ship names
• Her Majesty's Ship or His Majesty's Ship or Submarine, the prefix of Royal Navy ship names (started in year 1789)
• Her Majesty's Station or His Majesty's Station, the prefix of Royal Navy base names
• Hellenic Mathematical Society, a Greek learned society
• Halbmastwurf-Sicherung, a knot also called Munter hitch, and the type of carabiner used with it
• Harakat Mujtama' as-Silm (Movement of Society for Peace), an Algerian Islamist political party
• Harvard Medical School
• Haslemere Musical Society ^Link
• Hazardous materials safety
• Hazrat Mohammed (Salaal Laahu Alaihi Wa Salaam)
• Headend management station
• Health monitoring system
• Heavy melting steel
• Helmet-mounted sight
• Hendrick Motorsports
• Her Majesty Shufflers (Melbourne Shuffle)
• National Rail station code of Helmsdale railway station, Scotland
• Hero-Martyr Syndrome
• Hidden Markov source in statistical modelling
• Highly migratory species
• High Mountain Software
• High Mowing School, a private coeducational Waldorf boarding school located in Wilton, New Hampshire
• Hind Mazdoor Sabha, a trade union in India
• Historical Maritime Society, a British naval reenactment society
• Historical Metallurgy Society ^Link
• Home media server
• Homestead Miami Speedway
• Hour-Minute-Second
• Hull mounted sonar
• Hybrid management sublayer
• Hydrologic Modeling System - HEC HMS

Management systems

• Hospital management system
• Hospital Management System for IIT Bombay
• Hotel management system
• Hypertext management system

Middle schools

• Hichborn Middle School, Howland, Maine
• Hackensack Middle School, Hackensack, New Jersey
• Hamden Middle School, Hamden, Connecticut
• Hammarskjold Middle School, East Brunswick, New Jersey
• Hampstead Middle School, Hampstead, New Hampshire
• J.E. Harrison Middle School, Pittsburgh, Pennsylvania
• Hempstead Middle School, Hempstead, Texas
• Artie Henry Middle School, Cedar Park, TX, also known as Henry Middle School. (HMS)
• Heritage Middle School, Minnesota
• Herricks Middle School, Albertson, New York.
• Highland Middle School, Libertyville, Illinois
• Hinsdale Middle School,Hinsdale, Illinois
• Hopewell Middle School, Georgia
• Horton Middle School, Pittsboro, NC
• Huntington Middle School, Warner Robins, Georgia
• Henry E. Huntington Middle School, San Marino, California